Action of gibberellic acid (GA3) on dormancy and activity of alpha-amylase in rice seeds

To evaluate the effectiveness of gibberellic acid (GA3) in breaking rice seed dormancy and the use of alpha-amylase enzyme activity as an indicator of the dormancy level, seed from the intensively dormant irrigated cultivar Urucuia were used. The seeds were submitted to a pre-drying process in a forced air circulation chamber under 40ºC during 7 days and submersed in 30 mL of GA3 solution under 0, 10, 30 and 60 mg/L H2O concentrations, during 2, 24 and 36 hours. After the treatments, the alpha-amylase activity was determined by using the polyacrilamide electrophoresis and spectrophotometry. At the same time, the germination test was made. The results indicated a gain in germination and in alpha-amylase activity in higher concentrations and soaking time of seeds in GA3. These observations support the conclusion that soaking seed in 60 mg GA3/L during 36 hours can be used as a quick and efficient treatment in breaking rice seed dormancy and is equivalent to the forced air circulation chamber at 40ºC during 7 days. The alpha-amylase enzyme activity proved to be as an efficient marker of the seeds dormancy level.

Seed moisture range in a soybean plant

It is common to see in any soybean plant that seeds reach maturity at different times. Thus the objective of the present study was to determine the magnitude of the seed moisture range at different stages of maturation in a soybean plant. The field study was conducted in a tropical region in the state of Mato Grosso - Brazil, established with foundation seeds of the MTBR-45 cultivar, and at flowering, 100 plants were marked at the same maturity stage. Harvesting began when seeds still were at high moisture content (MC). At each of eight harvesting times, during 16 days, all pods from two plants were harvested and the seeds from each pod were hand threshed individually and determined the moisture content . The results revealed that there is a great distribution of seed MC in a soybean plant, where at physiological maturity, the magnitude can reach more than 30 percentage points. Also, even with an average MC below 12%, there were more than 20 % of the seeds with MC above 13% and some seeds at this point had been waiting to be harvested for more than a week. The following conclusions and/or recommendations can be taken: 1- The great seed MC range in a soybean seed lot harvested at field maturity leads to the presence of seeds susceptible to mechanical damage and with MC unsafe for adequate storage; 2 - It is recommended that harvesting be accomplished when the seeds are in the 15-18% MC range, in order to minimize field deterioration and the percentage of seeds with high MC; 3- Drying is recommended, even when soybean seeds are in their average MC safe for storage.

Soil seed bank variation patterns according to environmental factors in a natural grassland

This research aimed to determine the soil seed bank and its relationship with environmental factors that have an influence in the distribution of the vegetation above the ground in an excluded area of natural grassland in the South of Brazil. Most of the 122 identified species in the seed bank were perennials. Data analysis indicated three distinct community groups, according to the size and composition of the soil seed bank in lowlands with permanent wet soils, in lowlands and in other areas. In general, lowlands were characterized by low-fertility soils, high moisture and aluminum contents, being spatially homogeneous habitats and, therefore, more restricted to vegetation heterogeneity than other parts of the relief. Environmental factors most associated with soil seed bank size and composition were relief position and their co-related soil variables such as: soil moisture content, potassium content, organic matter, basic saturation of cation exchange soil capacity, exchangeable basics sum of the soil and clay soil content. According to that, relief position, associated with combined effects of soil chemical properties related to it, determines the observed variation pattern of the soil seed bank, as a reflection of the vegetation above the area.

Quantitative characteristics of fruits and seeds of Pouteria pachycarpa Pires - Sapotaceae

Pouteria pachycarpa is a tree species, found in the Brazilian Amazon and Bolivia whose wood has been exploited from the native forest. The present research describes the quantitative characteristics of fruits and seeds and quantifies the seed germination of this species. The fruit and seed color were characterized and measurements taken of the mass, length, diameter and number of seeds per fruit, the seed length, width and thickness, the germination percentage, abnormal seedlings and dead seeds. Sowing was carried out on a substrate containing sand and sawdust (1:1), in four replications of 50 seeds. The predominant fruit and seed colors were vivid yellowish orange (9YR) and dark grayish brown (6YR), respectively. Fruit mass, length and diameter ranged from 37.7 to 192.4g, 41.3 to 87.3mm and 39.7 to 71.7mm, respectively. Fruits had from two to seven seeds, and 42.6% were damaged by insects. Seed length, width and thickness ranged from 22.4 to 35.2mm, 9.7 to 15.5mm and 5.5 to 10.8mm, respectively. Seedling emergence began 18 days after sowing. Maximum germination, 86%, was recorded 33 days after sowing. The germination curve was sigmoid, similar to the majority of species. The percentage of abnormal seedlings and dead seeds were 3% and 11%, respectively. Both fruits and seeds show great variation in quantitative characteristics and the germination is slow and non-uniform.

Physiological quality of wheat seeds submitted to saline stress

The objective of this experiment was to determine the influence of different salt levels (zero, 15, 30, 45 and 60mM NaCl) on seed physiological quality of two wheat cultivars (BRS 177 and BRS 179). SUMMARIZE METHODOLOGY. The results allow the following conclusions: the physiological quality (germination and vigor) of wheat seeds, cultivars BRS 179 and BRS 177, decrease with the increase of the salinity. The wheat seeds cv. BRS 179 performs better than BRS 177, mainly in higher salt concentrations (³ 45mM of NaCl). The electric conductivity of wheat seeds increases in function of the increment of the saline concentrations.

Heliotropism and water availability effects on flowering dynamics and seed production in Macroptilium lathyroides

The experiment was carried out in pots in a glasshouse, with one plant per pot and nine repetitions per treatment. The treatments consisted of free or restricted leaves, submited to 90-100% or 60-70% soil field capacity (FC). Only independent effects of water availability or leaf movement were observed on yield components. Plants under well-watered conditions and with freely orienting leaves were taller, and had a larger number of ramifications. The greater development favored the setting of a higher number of inflorescences per plant in these treatments. This behavior resulted in a high number of flowers, green and mature legumes per plant, thus resulting in high seed production which was the most evident response to water availability. Although individual seed weight was higher in the water stress treatment, total seed production was higher for well-watered plants, with no statistically significant effect of leaf movements.

Methods of overcoming dormancy in Schizolobium amazonicum Huber ex Ducke (Leguminosae - Caesalpinioideae) seeds

Seed dormancy is a frequent phenomenon in tropical species, causing slow and non-uniform germination. To overcome this, treatments such as scarification on abrasive surface and hot water are efficient. The objective of this study was to quantify seed germination with no treatment (Experiment 1) and identify an efficient method of breaking dormancy in Schizolobium amazonicum Huber ex Ducke seeds (Experiment 2). The effects of manual scarification on electric emery, water at 80ºC and 100ºC and manual scarification on wood sandpaper were studied. Seeds were sown either immediately after scarification or after immersion in water for 24h in a sand and sawdust mixture. Germination and hard seed percentages and germination speed were recorded and analyzed in a completely randomized design. Analysis of germination was carried out at six, nine, 12, 15, 18, 21 and 24 days after sowing as a 4x2 factorial design and through regression analysis. Treatment means of the remaining variables were compared by the Tukey test. Seed germination with no treatment started on the 7th day after sowing and reached 90% on the 2310th day (Experiment 1). Significant interaction between treatments to overcome dormancy and time of immersion in water was observed (Experiment 2). In general, immersion in water increased the germination in most evaluations. The regression analyses were significant for all treatments with exception of the control treatment and immersion in water at 80ºC. Germination speed was higher when seeds were scarified on an abrasive surface (emery and sandpaper) and, in these treatments, the germination ranged from 87% to 96%, with no hard seeds. S. amazonicum seeds coats are impermeable to water, which hinders quick and uniform germination. Scarification on electric emery followed by immediate sowing, scarification on sandpaper followed by immediate sowing and sowing after 24h were the most efficient treatments for overcoming dormancy in S. amazonicum seeds.

Physiological quality of barley seeds submitted to saline stress

The objective of the experiments was to determine the influence of the effects of different salt levels (zero, 15, 30, 45 and 60mM NaCl) on the physiological quality of seeds of two barley cultivars (BRS 195 and AF 98067). Assays were conducted to evaluate salt stress on germination and vigor. The germination and germination rate of the barley seeds decreased as salt levels increased, reducing the seed viability and vigor. The salinity affected the membrane integrity, mainly in AF 98067 that showed more sensitivity to salt stress.

Eletrical conductivity and deterioration of soybean seeds exposed to different storage conditions

Research with soybean seeds has revealed that the results of the electrical conductivity test may be influenced by storage temperature, particularly low temperature, such as 10ºC, suggesting that seed deterioration at low storage temperatures does not seem to be directly related to the loss of the cell membrane integrity. This study was conducted with seeds of two soybean cultivars with the objective of: a) studying the effect of different storage temperatures (10ºC; 20ºC; 25ºC; 20/10ºC and 25/10ºC) on the results of the electrical conductivity test; b) observing the behavior of fatty acids and carbohydrates during storage and studying its relation with the electrical conductivity results. Every three months, from a total of 18 months of storage, the physiological quality of seeds was evaluated using the germination, accelerated aging and electrical conductivity tests. Based on the obtained results, it can be concluded that the electrical conductivity test was not shown to be a good indicative of the deterioration process of seeds stored at low temperatures, and no direct relationship between changes in the fatty acids and carbohydrates and the behavior of the mentioned test for seeds stored at 10ºC was found.

Desiccation tolerance and DNA integrity in Eugenia pleurantha O. Berg. (myrtaceae) seeds

The aim of this study was to assess the desiccation tolerance and DNA integrity in Eugenia pleurantha seeds dehydrated to different moisture contents (MCs). Seeds extracted from mature fruits were submmited to drying in silica gel and evaluated at every five percentual points of decrease from the initial MC (35.5%, fresh weight basis). The effects of dehydration on seeds were verified through germination tests and DNA integrity assessment. Undried seeds achieved 87% germination, value reduced to 36% after being dried to 9.8% MC. When dried slightly more, to 7.4% MC, seeds were no longer able to germinate, suggesting an intermediate behavior in relation to desiccation tolerance. It was observed DNA degradation in seeds with 7.4% MC, which might have contributed to the loss of seed germination.

Desiccation tolerance and dna integrity in Eugenia pleurantha o. berg. (Myrtaceae) seeds

The aim of this study was to assess the desiccation tolerance and DNA integrity in Eugenia pleurantha seeds dehydrated to different moisture contents (MCs). Seeds extracted from mature fruits were dried in silica gel and evaluated at every five percentual points of decrease from the initial MC (35.5%, fresh weight basis). The effects of dehydration on seeds were verified through germination tests and DNA integrity assessment. Undried seeds achieved 87% germination, value reduced to 36% after being dried to 9.8% MC. When dried slightly more, to 7.4% MC, seeds were no longer able to germinate, suggesting an intermediate behavior in relation to desiccation tolerance. DNA degradation was observed in seeds with 7.4% MC, which might have contributed to the loss of seed germination.

Lolium multiflorum seeds in the soil: I. Soil seed bank dynamics in a no til system

The objective of the study was to characterize annual ryegrass seed population dynamics, managed for natural re-sowing, in no til systems in rotation with soybean, in different chronosequences An area was cultivated for two years with soybean, left as fallow land for the next two years and then cultivated again with soybean for the next two years. The four chronosequences represented different management periods, two with soybean (6 and 8 years old) and the other two resting (3 and 9 years old). Soil samples were taken every month during one year and divided into two depths (0-5 and 5-10 cm). Vegetation dynamics were also evaluated (number of plants, inflorescences and seedlings). Soil seed bank (SSB) dynamics showed structural patterns in time, with a "storage period" in summer, an "exhausting period" during autumn and a "transition period" in winter and spring. Pasture establishment by natural re-sowing was totally dependent on the annual recruitment of seeds from the soil. The influence of the management practices on the SSB was more important than the number of years that these practices had been implemented. Places where soybean was sown showed the largest SSBs. Most of the seeds overcame dormancy and germinated at the end of the summer and beginning of the autumn, showing a typically transitory SSB, but with a small proportion of persistent seeds

Evaluation of lignin content of soybean seed coat stored in a controlled environment

Breeding soybean for high seed quality is an important approach for developing cultivars for tropical regions, and the lignin content in the seed coat is one of the screening parameters for this trait. Considering that many breeding lines are evaluated in each growing season using the presently recommended method for lignin determination, a long period is required for the evaluation of the whole breeding program. This time limitation may influence lignin content assessment, if lignin is degraded during storage. This research reported was designed to determine whether lignin was degraded in the seed coat of soybean seed cultivars stored for one year in a controlled environment (10°C temperature and 50% air relative humidity). Seeds of 12 selected soybean cultivars that had a range in seed coat lignin content were evaluated. Seeds were hand harvested just after physiological maturity and evaluated for seed coat lignin content at harvest and after one year of storage in a cold room (10°C and 50% RH). The lignin content in seed coats differed significantly among cultivars in both analyses, but for both results the sequence of cultivar classification and the lignin content values of each cultivar did not change. A regression analysis of lignin content at harvest and after one year of storage indicated a direct relationship between both lignin determinations suggesting no differences between the lignin content of each cultivar due to prolonged storage (r² = 0.98***). This indicates that the lignin determination in the soybean seed coat can be performed over a long time period without any bias due to change in its content.

Performance of different drying methods and their effects on the physiological quality of grain sorghum seeds (S. bicolor (L.) Moench)

This experiment viewed to evaluate the physiological quality of grain sorghum seeds as well as to determine the respective drying curve of each of three drying methods. The seeds harvested at 18.9%, 18.1%, and 18.2% of moisture content were submitted to the following drying methods : a) under natural conditions, b) an intermittent dryer in which the combustion of firewood was the source of caloric energy, and c) a stationary dryer in which the source of caloric energy was the burning of liquefied petroleum gas. The experimental design was a completely randomized one with 25 repetitions of one hundred seeds each. The water contents and weight of one thousand seeds were evaluated. Seeds physiological quality was evaluated by germination and vigor tests. Seed drying rates were of 0.11, 1.25, and 0.55 percent points per hour (pph -1) for the natural, intermittent and stationary drying methods, respectively. The intermittent treatment permits the highest loss of water in the shortest period of time, and germination and vigor remaining unchanged.

Changes in gene expression during drying and imbibition of desiccation sensitive Magnolia ovata (A. St.-Hil.) spreng. seeds

Seeds of Magnolia ovata were dried to different water contents to assess the viability and transcript abundance of genes related to seed development, cell cycle, cytoskeleton and desiccation tolerance.The expression of development, cell cycle and cytoskeleton relative genes (ABI3, CDC2-like and ACT2) alone could not explain the germination behaviour of M. ovata seeds in relation to drying damage. Irrespective of their initial water content, the seeds performed in the same way during the initial period of germination and the deleterious effects of desiccation only occurred in later stages. Expression of PKABA1, sHSP17.5 and 2-Cys-PRX did not show a relationship with desiccation. However, the expression patterns of PKABA1 and sHSP17.5 suggested the participation of these genes in protective mechanisms during the imbibition of M. ovata seeds.